International Journal of Pediatric Otorhinolaryngology 78 (2014) 268–271
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International Journal of Pediatric Otorhinolaryngology journal homepage: www.elsevier.com/locate/ijporl
Computed tomography demonstrates abnormalities of contralateral ear in subjects with unilateral sensorineural hearing loss§ Sonya Marcus a, Christopher T. Whitlow b, James Koonce c, Michael E. Zapadka b, Michael Y. Chen b, Daniel W. Williams III.d, Meagan Lewis e, Adele K. Evans e,* a
New York University Langone Medical Center, Department of Otolaryngology, 550 First Avenue, NBB 5E5, New York, NY 10016, United States Department of Radiology, Wake ForestTM School of Medicine, Medical Center Boulevard, Winston-Salem, NC 27157, United States c Mountain Empire Radiology, 1301 Sunset Drive Suite 3, Johnson City, TN 37604, United States d Head & Neck Radiology, Neuroradiology, Department of Radiology, Wake ForestTM School of Medicine, Medical Center Boulevard, Winston-Salem, NC 27157, United States e Department of Otolaryngology, Wake ForestTM School of Medicine, Medical Center Boulevard, Winston-Salem, NC 27157, United States b
A R T I C L E I N F O
A B S T R A C T
Article history: Received 12 September 2013 Received in revised form 15 November 2013 Accepted 17 November 2013 Available online 25 November 2013
Purpose: Prior studies have associated gross inner ear abnormalities with pediatric sensorineural hearing loss (SNHL) using computed tomography (CT). No studies to date have specifically investigated morphologic inner ear abnormalities involving the contralateral unaffected ear in patients with unilateral SNHL. The purpose of this study is to evaluate contralateral inner ear structures of subjects with unilateral SNHL but no grossly abnormal findings on CT. Materials and methods: IRB-approved retrospective analysis of pediatric temporal bone CT scans. 97 temporal bone CT scans, previously interpreted as ‘‘normal’’ based upon previously accepted guidelines by board certified neuroradiologists, were assessed using 12 measurements of the semicircular canals, cochlea and vestibule. The control-group consisted of 72 ‘‘normal’’ temporal bone CTs with underlying SNHL in the subject excluded. The study-group consisted of 25 normal-hearing contralateral temporal bones in subjects with unilateral SNHL. Multivariate analysis of covariance (MANCOVA) was then conducted to evaluate for differences between the study and control group. Results: Cochlea basal turn lumen width was significantly greater in magnitude and central lucency of the lateral semicircular canal bony island was significantly lower in density for audiometrically normal ears of subjects with unilateral SNHL compared to controls. Conclusion: Abnormalities of the inner ear were present in the contralateral audiometrically normal ears of subjects with unilateral SNHL. These data suggest that patients with unilateral SNHL may have a more pervasive disease process that results in abnormalities of both ears. The findings of a cochlea basal turn lumen width disparity >5% from ‘‘normal’’ and/or a lateral semicircular canal bony island central lucency disparity of >5% from ‘‘normal’’ may indicate inherent risk to the contralateral unaffected ear in pediatric patients with unilateral sensorineural hearing loss. ß 2013 Elsevier Ireland Ltd. All rights reserved.
Keywords: Temporal bone anatomy Unilateral sensorineural hearing loss Pediatric hearing loss Inner ear abnormalities Bony island lucency Temporal bone computed tomography
1. Introduction Computed tomography (CT) of the temporal bone has proven to be an invaluable diagnostic tool in the evaluation of children with unilateral sensorineural hearing loss (USNHL) [1], providing insight into etiology and impacting both the prognosis and
§ This original work was presented at the podium at the American Society for Pediatric Otolaryngology (ASPO) meeting in Washington, DC/Arlington, VA in April, 2013. * Corresponding author. Tel.: +1 336 716 3684; fax: +1 336 716 3857. E-mail address: [email protected] (A.K. Evans).
0165-5876/$ – see front matter ß 2013 Elsevier Ireland Ltd. All rights reserved. http://dx.doi.org/10.1016/j.ijporl.2013.11.020
management of those children affected [2]. Prior studies have shown that as many as 35% of patients with USNHL demonstrated inner ear malformations evident on CT within the affected ear [3], and as imaging quality continues to improve, previously unrecognized abnormalities are increasingly detected. Less attention has been paid to the contralateral ear in patients with USNHL, yet there is evidence that patients with USNHL may have inner ear abnormalities within their normal hearing ear as well. This has been described in cases of bilateral EVA in which only one ear demonstrated hearing impairment at the time of imaging [4]. These findings have important implications, as USNHL may represent an early manifestation of bilateral disease in certain
S. Marcus et al. / International Journal of Pediatric Otorhinolaryngology 78 (2014) 268–271
patients. In our study, we evaluate the contralateral ear in children with idiopathic USNHL using temporal bone CT.
Table 1 Demographic composition of the subject group compared to the study group.
2. Materials and methods 2.1. Subjects This HIPAA-compliant IRB-approved retrospective study analyzed temporal bone CT scans of children aged 0–18 years who underwent evaluation for hearing loss at a tertiary care medical center from 2006 to 2012. The study group consisted of 25 children (12 females and 13 males) diagnosed with USNHL with no audiometric abnormality in the contralateral ear, and CT scans of these ears interpreted as ‘‘normal’’ by board-certified neuroradiologists. We excluded all children with a diagnosis of USNHL attributed to: conductive hearing loss; auditory neuropathy; SNHL due to recurrent otitis media, meningitis, maternal cytomegalovirus infection, rubella, toxoplasmosis, aminoglycoside exposure, ECMO, intraventricular hemorrhage, an autoimmune process or a syndromic disease. Patients ranged in age from 4 months to 17 years (average = 8 years). The control group consisted of 72 ears in pediatric subjects who underwent evaluation with temporal bone CT scanning, i.e. for conductive hearing loss. All subjects had audiograms that were reviewed by a certified clinical audiologist to rule out underlying SNHL. 38 subjects were included: 18 females (36 ears) and 20 males (36 ears). Four of the subject ears were excluded from the study due to inner ear erosion from cholesteatoma or mixed hearing loss. Patients ranged in age from 2 to 18 years old (average = 10 years).
269
Demographic
Subjects
Controls
Mean age (years) [range] Sex (# of ears included) Male Female Race (# of ears included) Asian African-American Burmese Caucasian Hispanic Unknown Other
8 25 13 12 25 0 5 0 12 7 1 –
10 72 36 36 72 2 2 2 56 7 1 2
[0.3–17] (52%) (48%)
(20%) (48%) (28%) (4%)
[2–18] (50%) (50%) (2.7%) (2.7%) (2.7%) (77.7%) (9.7%) (1.4%) (2.7%)
on Phillips PACS (picture archiving and communications systems) terminals by one radiologist. Inter-rater reliability was established by random sampling review by two other neuroradiologists. 2.4. Statistics A one-way between group multivariate analysis of covariance (MANCOVA) was performed for each dependent measure of the inner ear, with group as the independent variable (group 1: audiometrically normal ears of subjects with USNHL; group 2: sensorineural hearing loss excluded controls) and sex (male, female) as a covariate. Sex was previously determined to be a significant covariate [5]. All statistical analyses were performed with statistical software (SPSS, version 16.0; SPSS, Chicago, Ill).
2.2. Measurements
3. Results
Measurements of semicircular canals, cochlea and vestibule were made on temporal bone CT scans as previously described [5]. These measurements were chosen as they have demonstrated utility in identifying subtle inner ear abnormalities in prior studies [2,6–10].
A total of 97 ears were assessed: 25 normal-hearing contralateral ears in subjects with unilateral sensorineural hearing loss and 72 control ears in subjects with no history of sensorineural hearing loss. The mean age at study, the sex and the race demographics are recorded in Table 1. MANCOVA, controlling for sex, revealed statistically significant differences between inner ear measurements from audiometrically normal ears of subjects with USNHL compared to controls, as follows (as designated with an * in Table 2, with full measurement details):
2.3. Computed tomography of the temporal bone analysis All temporal bone studies were non-contrast enhanced studies performed using standard technique on GE1 64-slice scanners with slice-thickness of 0.625 mm. The studies were acquired in the axial plane with coronal images reformatted from the axial data. Images were acquired with a focused field of view ranging from 20 to 24 cm and with a high-resolution bone algorithm and reviewed
(1) Cochlea basal turn lumen width was 6.54% wider in the SNHL study group (mean SD; 1.91 .29) compared to controls (mean SD; 1.78 .21) [F(1,94) = 5.372, p = .023].
Table 2 Summary of temporal bone anatomical measurements in the normal-hearing ear of subjects with contralateral unilateral sensorineural hearing loss compared to subjects without sensorineural hearing loss. Statistical significance was identified for the cochlear basal turn lumen width and the central lucency of the bony island of the lateral semicircular canal, both highlighted with the asterisk (*). Measurement parameter
Subject ear Mean
LSCC bony island width (mm) SSCC bony island width (mm) Cochlear height (mm) Cochlear length (mm) Cochlear basal turn lumen width* (mm) Bony canal [aperture] for the cochlear nerve width (mm) Bony canal [aperture] for the cochlear nerve height (mm) Vestibular width (mm) Vestibular length (mm) Central lucency of the bony island of the LSCC* (HU) Cochlear height [coronal] (mm) Vestibule oblique diameter (mm)
Control ear SD
3.94 5.43 4.64 5.88 1.91 2.38 1.16 3.18
0.64 0.64 0.42 0.32 0.29 0.27 0.25 0.22
6.16 1716 5.09 5.41
0.51 182 0.47 0.48
Range 2.9–5.2 4.5–6.7 4.0–5.9 5.4–6.4 1.2–2.5 1.8–2.9 0.7–1.6 2.7–3.6 5.2–7 1009–2023 3.9–5.8 4.4–6.1
Mean
SD
4.12 5.32 4.49 5.91 1.78 2.42 1.11 3.09
0.46 0.49 0.38 0.38 0.21 0.43 0.21 0.27
5.98 1805 5.09 5.43
0.38 106 0.60 0.39
Range 3.0–5.9 4.5–6.4 3.5–5.6 5.1–6.7 1.2–2.3 1.4–3.6 0.7–1.7 2.4–3.5 5.1–7 1577–2019 3.4–6 4.4–6.3
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S. Marcus et al. / International Journal of Pediatric Otorhinolaryngology 78 (2014) 268–271
(2) Central lucency of the LSCC bony island was 4.98% less dense in the SNHL study group (mean SD; 1715.58 182.11) compared to controls (mean SD; 1805.44 105.82) [F(1,94) = 8.991, p = .003].
No statistically significant between-group differences were identified for any other inner ear measurements (p > .05); however, there was a trend toward statistical significance for vestibular width, which was 3.00% wider in the SNHL group (mean SD; 6.16 .51) compared to controls (mean SD; 5.98 .38) [F(1,94) = 3.404, p = .068]. 4. Discussion Few studies address the normal hearing ear in patients with USNHL, yet there is increasing evidence that in certain patients, USNHL may represent an early manifestation of bilateral disease [11]. We reviewed CT scans of children with otherwise idiopathic USNHL to determine whether differences between USNHL contralateral ears and controls could be detected via measurement by calipers. Comparative measurements were acquired for 12 dimensions, including: LSCC bony island width, SSCC bony island width, cochlear height, cochlear length, cochlea basal turn lumen width, cochlear aperture width, cochlea aperture height, vestibular width, vestibular length, central lucency of the LSCC bony island, cochlea height (coronal), and vestibule oblique diameter (coronal). In the evaluation of children with USNHL, progression of hearing loss within the affected ear and incidence of hearing loss within the contralateral normal hearing ear are of significant interest. We did not evaluate progression within the affected ear, but prior studies report rates as varied as 0.75–21% [11–13]. Regarding new-onset hearing loss in the contralateral ear, a 2009 study by Uweira et al. [11] cited an incidence of 10.6% in their patient population at an average follow-up of 12 months. Insight into which children may develop bilateral disease is of significant interest, as the anticipatory guidance and hearing loss management of these children could be affected. Temporal bone imaging is recommended in the evaluation of all children with USNHL [14], and CT has shown utility in identifying bilateral disease in children with unilateral hearing deficits. In a study by Bamiou et al. [4], evaluation by CT was instrumental in identifying bilateral EVA in two children with USNHL, prompting further evaluation and referral to hearing preservation counseling. In our study, we similarly analyzed CT imaging, but only included patients with ‘‘normal’’ imaging as interpreted by board-certified neuroradiologists. Thus, gross abnormalities, including EVA were excluded. Additionally, we took measurements via electronic calipers on high resolution CT scans (0.625 mm slice-thickness) which may have detected findings that would have otherwise been missed. The data in our study revealed statistically significant differences between USNHL contralateral ears and controls. We found that the cochlea basal turn lumen width was significantly greater in magnitude (6.54% wider) and central lucency of the lateral semicircular canal bony island was significantly lower in density (4.98% less dense) for audiometrically normal ears of subjects with USNHL compared to controls. Although Uweira et al. [11] did not find a significant correlation between abnormalities on temporal bone CT and hearing loss development within the contralateral ear, that study evaluated only two measurements that have an established association as a gross anatomical anomaly and was not designed to look at the measurements themselves. Further longitudinal investigation within this patient population remains necessary to evaluate which patients are at an increased risk of developing bilateral disease.
There are several limitations to this study. Firstly, the control population included children who received temporal bone CT scans in the evaluation of conductive hearing loss (CHL), and not children with normal hearing, as it was difficult to find children who received CT scans for an indication other than hearing loss. However, conductive hearing loss should not impact inner ear structures, and SNHL or mixed hearing loss was excluded in these patients by audiogram. Secondly, we did not analyze MRI findings within our study. This comparative utility remains a topic of investigation. Simons, Mandell and Arjmand supported the use of CT as the preferred imaging study in children with USNHL due to decreased logistical issues and a higher prevalence of positive findings [3]; Nakano found that MRI studies suggest cochlear nerve hypoplasia or aplasia may underly up to 50% of unilateral deafness cases [15], and Clemmens et al. found that in the absence of MRI this can be predicted from bony cochlear nerve canal (cochlear aperture) measurements on CT [16]. We did not find this measurement to be a statistically significant measurement, hence it would suggest that our patient population did not have a large population of unilateral cochlear nerve aplasia or hypoplasia patients. Lastly, this study sample size was small as this was a retrospective study. A prospective or multi-center study would be the next step in investigation of the clinical utility of this data. Review of these subject cases with application of the new parameters (a >5% basal turn lumen width disparity from ‘‘normal’’ and/or a >5% LSSC bony island central lucency disparity from ‘‘normal’’) may give us a reference for prevalence of the findings in unaffected ears.
5. Conclusion Objectively measured abnormalities of the inner ear were present in the contralateral audiometrically normal ears of subjects with unilateral SNHL, suggesting that patients with unilateral SNHL may have a more pervasive disease process that results in abnormalities of both ears. The findings of a cochlea basal turn lumen width disparity >5% from ‘‘normal’’ and/or a lateral semicircular canal bony island central lucency disparity of >5% from ‘‘normal’’ may indicate inherent risk to the contralateral unaffected ear in pediatric patients with unilateral sensorineural hearing loss. References [1] D.A. Preciado, L.H. Lim, A.P. Cohen, C. Madden, D. Myer, C. Ngo, et al., A diagnostic paradigm for childhood idiopathic sensorineural hearing loss, Otolaryngol. Head Neck Surg. 131 (2004) 804–809. [2] J.E. McClay, R. Tandy, K. Grundfast, S. Choi, G. Vezina, G. Zalzad, et al., Major and minor temporal bone abnormalities in children with and without congenital sensorineural hearing loss, Arch. Otolaryngol. Head Neck Surg. 128 (2002) 664– 671. [3] J.P. Simons, D.L. Mandell, E.M. Arjmand, Computed tomography and magnetic resonance imaging in pediatric unilateral and asymmetric sensorineural hearing loss, Arch. Otolaryngol. Head Neck Surg. 132 (2006) 186–192. [4] D.E. Bamiou, L. Savy, C. O’Mahoney, P. Phelps, T. Sirimanna, Unilateral sensorineural hearing loss and its aetiology in childhood: the contribution of computerized tomography in aetiological diagnosis and management, Int. J. Pediatr. Otorhinolaryngol. 51 (1999) 91–99. [5] S. Marcus, C.T. Whitlow, J. Koonce, M.E. Zapadka, M.Y. Chen, D.W. Williams 3rd, et al., Computed tomography supports histopathological evidence of vestibulocochlear sexual dimorphism, Int. J. Pediatr. Otorhinolaryngol. 77 (July (7)) (2013) 1118–1122. , http://dx.doi.org/10.1016/j.ijporl.2013.04.013. [6] D.D. Purcell, N. Fischbein, A.K. Lalwani, Identification of previously ‘‘undetectable’’ abnormalities of the bony labyrinth with computed tomography measurement, Laryngoscope 113 (2003) 1908–1911. [7] D. Purcell, J. Johnson, N. Fischbein, A.K. Lalwani, Establishment of normative cochlear and vestibular measurements to aid in the diagnosis of inner ear malformations, Otolaryngol. Head Neck Surg. 128 (2003) 78–87. [8] M.Y. Lan, J.Y. Shiao, C.Y. Ho, H.C. Hung, Measurements of normal inner ear on computed tomography in children with congential sensorineural hearing loss, Eur. Arch. Otorhinolaryngol. 266 (2009) 1361–1364.
S. Marcus et al. / International Journal of Pediatric Otorhinolaryngology 78 (2014) 268–271 [9] N. Tessier, T. Van Den Abbeele, G. Sebag, M. Elmaleh-Berges, Computed tomography measurements of the normal and the pathologic cochlea in children, Pediatr. Radiol. 40 (2010) 275–283. [10] G.M. Fatterpeker, S.K. Mukherji, J. Alley, Y. Lin, M. Castillo, Hypoplasia of the bony canal for the cochlear nerve in patients with congenital sensorineural hearing loss: initial observations, Radiology 215 (2000) 243–246. [11] T.C. Uweira, A. de Alarcon, J. Meinzen-Derr, A.P. Cohen, B. Rasmussen, G. Shott, et al., Hearing loss progression and contralateral involvement in children with unilateral sensorineural hearing loss, Ann. Otol. Rhino Laryngol. 118 (2009) 781– 785. [12] P.E. Brookhouser, D.W. Worthington, W.J. Kelly, Fluctuating and/or progressive sensorineural hearing loss in children, Laryngoscope 104 (1994) 958–964.
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[13] E. Vartiainen, S. Karjalainen, Prevalence and etiology of unilateral sensorineural hearing impairment in a finnish childhood population, Int. J. Pediatr. Otorhinolaryngol. 43 (1998) 253–259. [14] R.S. Yin, P.H. Tang, T.Y. Tan, Review of congenital inner ear abnormalities on CT temporal bone, Br. J. Radiol. 84 (2011) 859–863. [15] A. Nakano, Y. Arimoto, T. Matsunaga, Cochlear nerve deficiency and associated clinical features in patients with bilateral and unilateral hearing loss, Otol. Neurotol. 34 (April (3)) (2013) 554–558. [16] C.S. Clemmens, J. Guidi, A. Caroff, S.J. Cohn, J.A. Brant, A.M. Laury, et al., Unilateral cochlear nerve deficiency in children, Otolaryngol. Head Neck Surg. 149 (August (2)) (2013) 318–325.
Contents lists available at ScienceDirect
International Journal of Pediatric Otorhinolaryngology journal homepage: www.elsevier.com/locate/ijporl
Computed tomography demonstrates abnormalities of contralateral ear in subjects with unilateral sensorineural hearing loss§ Sonya Marcus a, Christopher T. Whitlow b, James Koonce c, Michael E. Zapadka b, Michael Y. Chen b, Daniel W. Williams III.d, Meagan Lewis e, Adele K. Evans e,* a
New York University Langone Medical Center, Department of Otolaryngology, 550 First Avenue, NBB 5E5, New York, NY 10016, United States Department of Radiology, Wake ForestTM School of Medicine, Medical Center Boulevard, Winston-Salem, NC 27157, United States c Mountain Empire Radiology, 1301 Sunset Drive Suite 3, Johnson City, TN 37604, United States d Head & Neck Radiology, Neuroradiology, Department of Radiology, Wake ForestTM School of Medicine, Medical Center Boulevard, Winston-Salem, NC 27157, United States e Department of Otolaryngology, Wake ForestTM School of Medicine, Medical Center Boulevard, Winston-Salem, NC 27157, United States b
A R T I C L E I N F O
A B S T R A C T
Article history: Received 12 September 2013 Received in revised form 15 November 2013 Accepted 17 November 2013 Available online 25 November 2013
Purpose: Prior studies have associated gross inner ear abnormalities with pediatric sensorineural hearing loss (SNHL) using computed tomography (CT). No studies to date have specifically investigated morphologic inner ear abnormalities involving the contralateral unaffected ear in patients with unilateral SNHL. The purpose of this study is to evaluate contralateral inner ear structures of subjects with unilateral SNHL but no grossly abnormal findings on CT. Materials and methods: IRB-approved retrospective analysis of pediatric temporal bone CT scans. 97 temporal bone CT scans, previously interpreted as ‘‘normal’’ based upon previously accepted guidelines by board certified neuroradiologists, were assessed using 12 measurements of the semicircular canals, cochlea and vestibule. The control-group consisted of 72 ‘‘normal’’ temporal bone CTs with underlying SNHL in the subject excluded. The study-group consisted of 25 normal-hearing contralateral temporal bones in subjects with unilateral SNHL. Multivariate analysis of covariance (MANCOVA) was then conducted to evaluate for differences between the study and control group. Results: Cochlea basal turn lumen width was significantly greater in magnitude and central lucency of the lateral semicircular canal bony island was significantly lower in density for audiometrically normal ears of subjects with unilateral SNHL compared to controls. Conclusion: Abnormalities of the inner ear were present in the contralateral audiometrically normal ears of subjects with unilateral SNHL. These data suggest that patients with unilateral SNHL may have a more pervasive disease process that results in abnormalities of both ears. The findings of a cochlea basal turn lumen width disparity >5% from ‘‘normal’’ and/or a lateral semicircular canal bony island central lucency disparity of >5% from ‘‘normal’’ may indicate inherent risk to the contralateral unaffected ear in pediatric patients with unilateral sensorineural hearing loss. ß 2013 Elsevier Ireland Ltd. All rights reserved.
Keywords: Temporal bone anatomy Unilateral sensorineural hearing loss Pediatric hearing loss Inner ear abnormalities Bony island lucency Temporal bone computed tomography
1. Introduction Computed tomography (CT) of the temporal bone has proven to be an invaluable diagnostic tool in the evaluation of children with unilateral sensorineural hearing loss (USNHL) [1], providing insight into etiology and impacting both the prognosis and
§ This original work was presented at the podium at the American Society for Pediatric Otolaryngology (ASPO) meeting in Washington, DC/Arlington, VA in April, 2013. * Corresponding author. Tel.: +1 336 716 3684; fax: +1 336 716 3857. E-mail address: [email protected] (A.K. Evans).
0165-5876/$ – see front matter ß 2013 Elsevier Ireland Ltd. All rights reserved. http://dx.doi.org/10.1016/j.ijporl.2013.11.020
management of those children affected [2]. Prior studies have shown that as many as 35% of patients with USNHL demonstrated inner ear malformations evident on CT within the affected ear [3], and as imaging quality continues to improve, previously unrecognized abnormalities are increasingly detected. Less attention has been paid to the contralateral ear in patients with USNHL, yet there is evidence that patients with USNHL may have inner ear abnormalities within their normal hearing ear as well. This has been described in cases of bilateral EVA in which only one ear demonstrated hearing impairment at the time of imaging [4]. These findings have important implications, as USNHL may represent an early manifestation of bilateral disease in certain
S. Marcus et al. / International Journal of Pediatric Otorhinolaryngology 78 (2014) 268–271
patients. In our study, we evaluate the contralateral ear in children with idiopathic USNHL using temporal bone CT.
Table 1 Demographic composition of the subject group compared to the study group.
2. Materials and methods 2.1. Subjects This HIPAA-compliant IRB-approved retrospective study analyzed temporal bone CT scans of children aged 0–18 years who underwent evaluation for hearing loss at a tertiary care medical center from 2006 to 2012. The study group consisted of 25 children (12 females and 13 males) diagnosed with USNHL with no audiometric abnormality in the contralateral ear, and CT scans of these ears interpreted as ‘‘normal’’ by board-certified neuroradiologists. We excluded all children with a diagnosis of USNHL attributed to: conductive hearing loss; auditory neuropathy; SNHL due to recurrent otitis media, meningitis, maternal cytomegalovirus infection, rubella, toxoplasmosis, aminoglycoside exposure, ECMO, intraventricular hemorrhage, an autoimmune process or a syndromic disease. Patients ranged in age from 4 months to 17 years (average = 8 years). The control group consisted of 72 ears in pediatric subjects who underwent evaluation with temporal bone CT scanning, i.e. for conductive hearing loss. All subjects had audiograms that were reviewed by a certified clinical audiologist to rule out underlying SNHL. 38 subjects were included: 18 females (36 ears) and 20 males (36 ears). Four of the subject ears were excluded from the study due to inner ear erosion from cholesteatoma or mixed hearing loss. Patients ranged in age from 2 to 18 years old (average = 10 years).
269
Demographic
Subjects
Controls
Mean age (years) [range] Sex (# of ears included) Male Female Race (# of ears included) Asian African-American Burmese Caucasian Hispanic Unknown Other
8 25 13 12 25 0 5 0 12 7 1 –
10 72 36 36 72 2 2 2 56 7 1 2
[0.3–17] (52%) (48%)
(20%) (48%) (28%) (4%)
[2–18] (50%) (50%) (2.7%) (2.7%) (2.7%) (77.7%) (9.7%) (1.4%) (2.7%)
on Phillips PACS (picture archiving and communications systems) terminals by one radiologist. Inter-rater reliability was established by random sampling review by two other neuroradiologists. 2.4. Statistics A one-way between group multivariate analysis of covariance (MANCOVA) was performed for each dependent measure of the inner ear, with group as the independent variable (group 1: audiometrically normal ears of subjects with USNHL; group 2: sensorineural hearing loss excluded controls) and sex (male, female) as a covariate. Sex was previously determined to be a significant covariate [5]. All statistical analyses were performed with statistical software (SPSS, version 16.0; SPSS, Chicago, Ill).
2.2. Measurements
3. Results
Measurements of semicircular canals, cochlea and vestibule were made on temporal bone CT scans as previously described [5]. These measurements were chosen as they have demonstrated utility in identifying subtle inner ear abnormalities in prior studies [2,6–10].
A total of 97 ears were assessed: 25 normal-hearing contralateral ears in subjects with unilateral sensorineural hearing loss and 72 control ears in subjects with no history of sensorineural hearing loss. The mean age at study, the sex and the race demographics are recorded in Table 1. MANCOVA, controlling for sex, revealed statistically significant differences between inner ear measurements from audiometrically normal ears of subjects with USNHL compared to controls, as follows (as designated with an * in Table 2, with full measurement details):
2.3. Computed tomography of the temporal bone analysis All temporal bone studies were non-contrast enhanced studies performed using standard technique on GE1 64-slice scanners with slice-thickness of 0.625 mm. The studies were acquired in the axial plane with coronal images reformatted from the axial data. Images were acquired with a focused field of view ranging from 20 to 24 cm and with a high-resolution bone algorithm and reviewed
(1) Cochlea basal turn lumen width was 6.54% wider in the SNHL study group (mean SD; 1.91 .29) compared to controls (mean SD; 1.78 .21) [F(1,94) = 5.372, p = .023].
Table 2 Summary of temporal bone anatomical measurements in the normal-hearing ear of subjects with contralateral unilateral sensorineural hearing loss compared to subjects without sensorineural hearing loss. Statistical significance was identified for the cochlear basal turn lumen width and the central lucency of the bony island of the lateral semicircular canal, both highlighted with the asterisk (*). Measurement parameter
Subject ear Mean
LSCC bony island width (mm) SSCC bony island width (mm) Cochlear height (mm) Cochlear length (mm) Cochlear basal turn lumen width* (mm) Bony canal [aperture] for the cochlear nerve width (mm) Bony canal [aperture] for the cochlear nerve height (mm) Vestibular width (mm) Vestibular length (mm) Central lucency of the bony island of the LSCC* (HU) Cochlear height [coronal] (mm) Vestibule oblique diameter (mm)
Control ear SD
3.94 5.43 4.64 5.88 1.91 2.38 1.16 3.18
0.64 0.64 0.42 0.32 0.29 0.27 0.25 0.22
6.16 1716 5.09 5.41
0.51 182 0.47 0.48
Range 2.9–5.2 4.5–6.7 4.0–5.9 5.4–6.4 1.2–2.5 1.8–2.9 0.7–1.6 2.7–3.6 5.2–7 1009–2023 3.9–5.8 4.4–6.1
Mean
SD
4.12 5.32 4.49 5.91 1.78 2.42 1.11 3.09
0.46 0.49 0.38 0.38 0.21 0.43 0.21 0.27
5.98 1805 5.09 5.43
0.38 106 0.60 0.39
Range 3.0–5.9 4.5–6.4 3.5–5.6 5.1–6.7 1.2–2.3 1.4–3.6 0.7–1.7 2.4–3.5 5.1–7 1577–2019 3.4–6 4.4–6.3
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S. Marcus et al. / International Journal of Pediatric Otorhinolaryngology 78 (2014) 268–271
(2) Central lucency of the LSCC bony island was 4.98% less dense in the SNHL study group (mean SD; 1715.58 182.11) compared to controls (mean SD; 1805.44 105.82) [F(1,94) = 8.991, p = .003].
No statistically significant between-group differences were identified for any other inner ear measurements (p > .05); however, there was a trend toward statistical significance for vestibular width, which was 3.00% wider in the SNHL group (mean SD; 6.16 .51) compared to controls (mean SD; 5.98 .38) [F(1,94) = 3.404, p = .068]. 4. Discussion Few studies address the normal hearing ear in patients with USNHL, yet there is increasing evidence that in certain patients, USNHL may represent an early manifestation of bilateral disease [11]. We reviewed CT scans of children with otherwise idiopathic USNHL to determine whether differences between USNHL contralateral ears and controls could be detected via measurement by calipers. Comparative measurements were acquired for 12 dimensions, including: LSCC bony island width, SSCC bony island width, cochlear height, cochlear length, cochlea basal turn lumen width, cochlear aperture width, cochlea aperture height, vestibular width, vestibular length, central lucency of the LSCC bony island, cochlea height (coronal), and vestibule oblique diameter (coronal). In the evaluation of children with USNHL, progression of hearing loss within the affected ear and incidence of hearing loss within the contralateral normal hearing ear are of significant interest. We did not evaluate progression within the affected ear, but prior studies report rates as varied as 0.75–21% [11–13]. Regarding new-onset hearing loss in the contralateral ear, a 2009 study by Uweira et al. [11] cited an incidence of 10.6% in their patient population at an average follow-up of 12 months. Insight into which children may develop bilateral disease is of significant interest, as the anticipatory guidance and hearing loss management of these children could be affected. Temporal bone imaging is recommended in the evaluation of all children with USNHL [14], and CT has shown utility in identifying bilateral disease in children with unilateral hearing deficits. In a study by Bamiou et al. [4], evaluation by CT was instrumental in identifying bilateral EVA in two children with USNHL, prompting further evaluation and referral to hearing preservation counseling. In our study, we similarly analyzed CT imaging, but only included patients with ‘‘normal’’ imaging as interpreted by board-certified neuroradiologists. Thus, gross abnormalities, including EVA were excluded. Additionally, we took measurements via electronic calipers on high resolution CT scans (0.625 mm slice-thickness) which may have detected findings that would have otherwise been missed. The data in our study revealed statistically significant differences between USNHL contralateral ears and controls. We found that the cochlea basal turn lumen width was significantly greater in magnitude (6.54% wider) and central lucency of the lateral semicircular canal bony island was significantly lower in density (4.98% less dense) for audiometrically normal ears of subjects with USNHL compared to controls. Although Uweira et al. [11] did not find a significant correlation between abnormalities on temporal bone CT and hearing loss development within the contralateral ear, that study evaluated only two measurements that have an established association as a gross anatomical anomaly and was not designed to look at the measurements themselves. Further longitudinal investigation within this patient population remains necessary to evaluate which patients are at an increased risk of developing bilateral disease.
There are several limitations to this study. Firstly, the control population included children who received temporal bone CT scans in the evaluation of conductive hearing loss (CHL), and not children with normal hearing, as it was difficult to find children who received CT scans for an indication other than hearing loss. However, conductive hearing loss should not impact inner ear structures, and SNHL or mixed hearing loss was excluded in these patients by audiogram. Secondly, we did not analyze MRI findings within our study. This comparative utility remains a topic of investigation. Simons, Mandell and Arjmand supported the use of CT as the preferred imaging study in children with USNHL due to decreased logistical issues and a higher prevalence of positive findings [3]; Nakano found that MRI studies suggest cochlear nerve hypoplasia or aplasia may underly up to 50% of unilateral deafness cases [15], and Clemmens et al. found that in the absence of MRI this can be predicted from bony cochlear nerve canal (cochlear aperture) measurements on CT [16]. We did not find this measurement to be a statistically significant measurement, hence it would suggest that our patient population did not have a large population of unilateral cochlear nerve aplasia or hypoplasia patients. Lastly, this study sample size was small as this was a retrospective study. A prospective or multi-center study would be the next step in investigation of the clinical utility of this data. Review of these subject cases with application of the new parameters (a >5% basal turn lumen width disparity from ‘‘normal’’ and/or a >5% LSSC bony island central lucency disparity from ‘‘normal’’) may give us a reference for prevalence of the findings in unaffected ears.
5. Conclusion Objectively measured abnormalities of the inner ear were present in the contralateral audiometrically normal ears of subjects with unilateral SNHL, suggesting that patients with unilateral SNHL may have a more pervasive disease process that results in abnormalities of both ears. The findings of a cochlea basal turn lumen width disparity >5% from ‘‘normal’’ and/or a lateral semicircular canal bony island central lucency disparity of >5% from ‘‘normal’’ may indicate inherent risk to the contralateral unaffected ear in pediatric patients with unilateral sensorineural hearing loss. References [1] D.A. Preciado, L.H. Lim, A.P. Cohen, C. Madden, D. Myer, C. Ngo, et al., A diagnostic paradigm for childhood idiopathic sensorineural hearing loss, Otolaryngol. Head Neck Surg. 131 (2004) 804–809. [2] J.E. McClay, R. Tandy, K. Grundfast, S. Choi, G. Vezina, G. Zalzad, et al., Major and minor temporal bone abnormalities in children with and without congenital sensorineural hearing loss, Arch. Otolaryngol. Head Neck Surg. 128 (2002) 664– 671. [3] J.P. Simons, D.L. Mandell, E.M. Arjmand, Computed tomography and magnetic resonance imaging in pediatric unilateral and asymmetric sensorineural hearing loss, Arch. Otolaryngol. Head Neck Surg. 132 (2006) 186–192. [4] D.E. Bamiou, L. Savy, C. O’Mahoney, P. Phelps, T. Sirimanna, Unilateral sensorineural hearing loss and its aetiology in childhood: the contribution of computerized tomography in aetiological diagnosis and management, Int. J. Pediatr. Otorhinolaryngol. 51 (1999) 91–99. [5] S. Marcus, C.T. Whitlow, J. Koonce, M.E. Zapadka, M.Y. Chen, D.W. Williams 3rd, et al., Computed tomography supports histopathological evidence of vestibulocochlear sexual dimorphism, Int. J. Pediatr. Otorhinolaryngol. 77 (July (7)) (2013) 1118–1122. , http://dx.doi.org/10.1016/j.ijporl.2013.04.013. [6] D.D. Purcell, N. Fischbein, A.K. Lalwani, Identification of previously ‘‘undetectable’’ abnormalities of the bony labyrinth with computed tomography measurement, Laryngoscope 113 (2003) 1908–1911. [7] D. Purcell, J. Johnson, N. Fischbein, A.K. Lalwani, Establishment of normative cochlear and vestibular measurements to aid in the diagnosis of inner ear malformations, Otolaryngol. Head Neck Surg. 128 (2003) 78–87. [8] M.Y. Lan, J.Y. Shiao, C.Y. Ho, H.C. Hung, Measurements of normal inner ear on computed tomography in children with congential sensorineural hearing loss, Eur. Arch. Otorhinolaryngol. 266 (2009) 1361–1364.
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